2 separate trades through one company, can i claim all expenses

Hi I have a client who operates as a Ltd and is a IT contractor. His wife is a yoga instructor and wants to know if he can put all income through the Co. I have so far advised him that this is possible, but then he asked if he can claim for all costs including training for the yoga lessons, basically the yoga will be making around a £10,000 loss in the first year, thereby redcing his overall profit by £10,000

I have been informed by someone who used to work for HMRC that my client will not be allowed to claim for expenses that means he make a loss on the separate trading activity. The client now wants to see any piece of legislation that says this, and through a thorough google session I can't for the life of me find this.

Any help or ideas will be greatly appreciated, even if it means I have told my client incorrect info so far.

Cheers

Tom